1. Field of the Invention
The invention relates to a pipe having variable cross section that is used to convey hot/cold flow medium.
2. Description of the Related Art
Conventional outdoor pipe networks of a centralized heating and cooling system consist of underground pipes including either polyurethane insulation layers or compound insulation layers, with advantages of cost-efficiency, ease of construction, short construction period, slight amount of maintenance and heat loss etc. Such pipe networks, however, cannot withstand steam with a temperature high as 150° C. or above that is probably liable to carbonate the polyurethane insulation layer, thus compromising its service life and insulation capability. As for the compound insulation layers, although a layer of high-temperature resistant paint is coated between the pipe and its polyurethane insulation layer, the aging and carbonation of polyurethane is mitigated to certain extent but the problem cannot be root out. In addition, this solution is not applicable to the indoor pipe networks of a centralized heating and cooling system.
For indoor pipe networks of a centralized heating and cooling system, glass fiber reinforced plastic, aluminum alloy, or stainless steel sheets are usually adopted to fabricate square tubes which are subsequently coated with insulation and protection layers and change its diameter or cross section in line with the flow-rate of any hot/cold flow medium passing through. As such a solution needs a great deal of space for installation, it is compulsory to raise the height of a room, thereby increasing the construction cost considerably and impairing its interior beauty seriously.